TypeORM，ManyToMany按类别id获取帖子(TreeEntity物化-路径)

Question

我试着像CMS一样按类别发布帖子。

例如，按类别分类的查询帖子A将包括所有附加在“类别A”上的帖子，以及附加到“类别A”的子类的帖子。

我真的不知道如何构建这个查询，所以任何帮助都是非常感谢的:)。

这是我的实体：

@Tree("materialized-path")
export class Category {
  @PrimaryGeneratedColumn()
    id: number;

    @Column()
    title: string;


    @ManyToMany((type) => Post, (post) => post.categories)
    posts: Post[];

    @Expose()
    @TreeChildren()
    children: Category[];

    @Expose()
    @TreeParent()
    parent: Category;
}

export class Post{
   @PrimaryGeneratedColumn()
    id: number;

    @Column()
    title: string;

    @ManyToMany((type) => Category, (category) => category.posts)
    @JoinTable()
    categories: Category[];
}

下面的SQL查询执行此任务(例如，类别id 1)

SELECT * FROM post WHERE id IN (
    SELECT postId FROM post_categories_category as postCat WHERE postCat.categoryId IN (
       SELECT id FROM category WHERE category.mpath LIKE "1.%" OR category.mpath LIKE "%.1.%"
    )
)

因此，问题是，如何将此SQL查询转换为typeORM查询？

Answer 1

我刚写了一个可能的快速解决方案。我测试过了它应该能正常工作。如果没有，就回答

@Entity()
@Tree("materialized-path")
export class Category extends BaseEntity {
  @PrimaryGeneratedColumn()
    id: number;

    @Column()
    title: string;

    @ManyToMany((type) => Post, (post) => post.categories)
    posts: Post[];

    @TreeChildren()
    children: Category[];

    @TreeParent()
    parent: Category;

    async getPosts(): Promise<Post[]> {
      const categories = await getConnection().getTreeRepository(Category).findDescendants(this); // gets all children
      categories.push(this); // adds parent

      const ids  = categories.map(cat => cat.id) // get an array of ids

      return await Post.createQueryBuilder('post')
        .distinct(true) // dont get duplicates (posts in two categories)
        .innerJoin('post.categories', 'category', 'category.id IN (:...ids)', {ids}) // get posts where category is in categories array
        .innerJoinAndSelect('post.categories', 'cat') // add all categories to selected post 
        .orderBy('post.id')
        .getMany()
    }
}

@Entity()
export class Post extends BaseEntity {
  @PrimaryGeneratedColumn()
   id: number;

   @Column()
   title: string;

   @ManyToMany((type) => Category, (category) => category.posts)
   @JoinTable()
   categories: Category[];
}

此方法使用querybuilders https://github.com/typeorm/typeorm/issues/2135#issuecomment-388801132。

以及findDescendants函数https://typeorm.io/#/tree-entities

希望这会有所帮助:)